Liquid crystal display including neighboring sub-pixel electrodes with opposite polarities in the same pixel

ABSTRACT

A liquid crystal display has a pixel array including first and second pixel electrodes. Each of the first pixel electrodes is divided into at least two first sub-pixel electrodes in two pixel areas sharing a corner or an edge. Similarly, each of the second pixel electrodes is divided into at least two second sub-pixel electrodes in two pixel areas sharing a corner or an edge. The polarities of the first and the second electrodes are opposite. The first and the second pixel electrodes are arranged alternatively to allow at least one first sub-pixel electrode and at least a second sub-pixel electrode to be located in each pixel area.

RELATED APPLICATIONS

This application claims priority to Taiwan Application Serial Number95109332, filed Mar. 17, 2006, which is herein incorporated byreference.

BACKGROUND

1. Field of Invention

The present invention relates to a liquid crystal display. Moreparticularly, the present invention relates to a liquid crystal displaycontaining sub-pixel electrodes.

2. Description of Related Art

Very wide viewing angles and high definition, among others, are theadvantages of a multi-domain vertical alignment (MVA) liquid crystaldisplay (LCD). Some slits and protrusions are formed on the innersurfaces of two transparent substrates in a conventional MVA LCD inwhich vertically aligned liquid crystal molecules are tiltedsymmetrically in opposite directions to compensate for viewing angles.

As disclosed in U.S. Pat. No. 6,922,183 (hereinafter, the “'183patent”), the lateral electric field applied to the slits on the innersurface of the transparent electrode of an MVA LCD has to be increased,so the liquid crystal molecules in the proximity of the slit can beinclined efficiently and liquid crystal molecular response time can bereduced. A pixel electrode is divided into two sub-pixel electrodes, andthus a pixel is divided into two sub-pixels. The two equipotentialsub-pixel electrodes with opposite polarities are electrically isolatedto each other by the slit. Lateral electric field is created on theslits to reduce response time of liquid crystal molecules.

However, the invention disclosed by the '183 patent requires each of twosub-pixel electrodes to be connected with a switch as a driving devicefor the corresponding sub-pixel. The number of driving devices for eachpixel is thus doubled. In addition, sub-pixels with opposite polaritiesmust have their own contact holes to conduct their own electronicsignals. When a pixel electrode is divided into several sub-pixelelectrodes, sub-pixel electrodes with the same polarity have to beconnected by additional wire in order to use one single switch as thedriving device. The additional wire will increase both the complexity ofelectric circuit and the difficulty of manufacturing process.

SUMMARY

An LCD is provided. The pixel electrode array of the LCD comprisesplural first pixel electrode and plural pixel electrode having oppositepolarities.

Each of the first pixel electrode comprises a first connecting part andtwo first sub-pixel electrodes located in two adjacent pixel areas. Eachfirst sub-pixel electrode has at least three corners. The two firstsub-pixel electrodes are diagonally connected through the firstconnecting part at respective corners of the two first sub-pixelelectrodes and separately located on one of the first pixel area and oneof the second pixel area located adjacently.

Similarly, each of the second pixel electrode comprises a secondconnecting part and two second sub-pixel electrodes located in twoadjacent pixel areas. Each second sub-pixel electrode has at least threecorners. The two second sub-pixel electrodes are diagonally connectedthrough the second connecting part at respective corners of the twosecond sub-pixel electrodes and separately located on one of the firstpixel area and one of the second pixel area located adjacently in such amanner that one of the two first sub-pixel electrodes and one of the twosecond sub-pixel electrodes are disposed side by side. Hence, each pixelarea comprises at least a first sub-pixel electrode and a secondsub-pixel electrode.

Plural first switches are located on the first pixel areas to controlthe first pixel electrodes, respectively. Plural second switches arelocated on the second pixel areas to control the second pixelelectrodes, respectively.

Accordingly, pixel electrode is divided into several structurallyconnected sub-pixel electrodes and only one driving switch device isrequired for one pixel electrode. Furthermore, the first sub-pixelelectrode and the second sub-pixel electrode are alternatively arranged.Same electric potential with opposite polarities can be applied toneighboring first pixel electrode and second pixel electrode. At leastone first sub-pixel electrode and one second sub-pixel electrode can beformed in each pixel area without additional signal line and drivingswitch device.

It is to be understood that both the foregoing general description andthe following detailed description are by examples, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thefollowing detailed description of the embodiment, with reference made tothe accompanying drawings as follows:

FIG. 1 illustrates the pixel array of an LCD according to an embodimentof the present invention;

FIG. 2 illustrates the pixel array of an LCD according to anotherembodiment of the present invention;

FIG. 3 illustrates the pixel array of an LCD according to anotherembodiment of the present invention; and

FIG. 4 illustrate a cross sectional view of a conventional LCD.

DETAILED DESCRIPTION

Accordingly, this invention provides an LCD, each pixel electrode of theLCD is divided into several sub-pixel electrodes. The two neighboringsub-pixel electrodes in the same pixel have opposite polarities. Thenumber of switch devices does not need to be increased. Onlyconventional signal line and switch device are required to obtain twoneighboring sub-pixel electrodes with opposite polarities in the samepixel. The LCD response time can thus be reduced.

Embodiment 1

FIG. 1 illustrates the pixel array of an LCD according to an embodimentof the invention. The pixel array 100 comprises pixel electrodes 110 and115. The pixel electrode 110 comprises two sub-pixel electrodes 110 aand 110 b. The sub-pixel electrodes 110 a, 110 b are formed in twoneighboring pixel areas 120 sharing an edge and diagonally connected toeach other through a connecting part 110 c. Similarly, pixel electrode115 comprises two sub-pixel electrodes 115 a and 115 b. The sub-pixelelectrodes 115 a and 115 b are formed in two neighboring pixel areas 120sharing an edge and diagonally connected to each other through aconnecting part 115 c. Therefore, a repeating unit of the pattern formedby the first sub-pixel electrodes 110 a, 110 b and the second sub-pixelelectrodes 115 a, 115 b is two first sub-pixel electrodes 110 a, 110 bin the two diagonal areas of a parallelogram and two second sub-pixelelectrodes 115 a, 115 b in the other two diagonal areas of theparallelogram.

Each of the above mentioned pixel area 120 is defined by a pair of scanlines 130 and a pair of data lines 140. A switch device 150 is formed inone corner of the pixel area 120. The switch device 150 of thisembodiment is a thin film transistor with a gate, a source and a drainconnected to the scan line 130, the data line 140, the sub-pixelelectrode 110 b or 115 b, respectively.

The pixel electrodes 110, 115 shown in FIG. 1 are formed on a switchdevice substrate alternatively. The two neighboring pixel electrodes110, 115 can be controlled to have opposite polarities, so that onepixel area 120 comprising two sub-pixel electrodes 110 b, 115 a (or 110a, 115 b) with opposite polarities can be obtained. The sub-pixelelectrodes 110 b, 115 a (or 110 a, 115 b) in one pixel area 120 belongto two different pixel electrodes 115, 110. Because, for example, thetwo sub-pixel electrodes (110 a, 110 b) or (115 a, 115 b) of one pixelelectrode 110 or 115 are still connected to each other, only one switchdevice is required to drive the pixel electrodes 110, 115. In addition,dot inversion method or any appropriate method can be used to allow thetwo neighboring pixel electrodes 110, 115 to have opposite polarities.

Embodiment 2

FIG. 2 illustrates the pixel array of an LCD according to anotherembodiment of the invention. FIG. 2 shows that pixel array 200 iscomposed of pixel electrodes 210 and 215. The pixel electrode 210 isdivided into three sub-pixel electrodes 210 a, 210 b, and 210 c. Thesub-pixel electrodes 210 a, 210 b, and 210 c are formed in the twoneighboring pixel areas 220 sharing an edge. The sub-pixel electrode 210b is diagonally connected to the sub-pixel electrodes 210 a and 210 cthrough connecting parts 210 d and 210 e. Similarly, the pixel electrode215 is divided into three sub-pixel electrodes 215 a, 215 b, and 215 c.The sub-pixel electrodes 215 a, 215 b, and 215 c are formed in the twoneighboring pixel areas 22 sharing an edge. The sub-pixel electrode 215b is diagonally connected to sub-pixel electrodes 215 a and 215 cthrough connecting parts 215 d and 215 e. Therefore, a repeating unit ofthe pattern formed by, for example, the first sub-pixel electrodes 210a, 110 b and the second sub-pixel electrodes 215 a, 215 b is two firstsub-pixel electrodes 210 a, 210 b in the two diagonal areas of aparallelogram and two second sub-pixel electrodes 215 a, 215 b in theother two diagonal areas of the parallelogram.

Each of the above mentioned pixel area 220 is defined by a pair of scanlines 230 and a pair of data lines 240. In addition, a switch device 250is formed in one corner of each pixel area 220. The switch device 250 inthis embodiment is a thin film transistor with a gate, a source and adrain connected to the scan line 230, the data line 240 and thesub-pixel electrode 210 c or 215 c, respectively.

As shown in FIG. 2, the pixel electrodes 210 and 215 are alternativelyformed on a switch device substrate. The three sub-pixel electrodes 210a, 215 b, 210 c (or 215 a, 210 b, 215 c) within the same pixel area 220have opposite polarities between the sub-pixel electrodes 210 a, 210 c(or 215 a, 215 c) and the sub-pixel electrode 215 b (or 210 b) when theneighboring pixel electrode 210 and the pixel electrode 215 haveopposite polarities. Although the sub-pixel electrodes 210 a, 210 b 210c of the pixel electrode 210 are arranged in two pixel areas 220 sharingan edge, the sub-pixel electrodes 210 a, 210 b, 210 c of the pixelelectrode 210 are connected through the connecting parts 210 d and 210e. Hence, only one switch device 250 is required for the pixel electrode210. Similarly, the sub-pixel electrodes 215 a, 215 b, 215 c of thepixel electrode 215 are also connected through the connecting parts 215d and 215 e; hence only one switch device 250 is required for the pixelelectrode 215. The way to obtain two neighboring pixel electrodes 210,215 with opposite polarities can be, for example, dot inversion.

Embodiment 3

FIG. 3 illustrates the pixel array of an LCD according to anotherembodiment of the invention. The pixel array 300 is composed of pixelelectrodes 310 and 315. The pixel electrode 310 is divided into twosub-pixel electrodes 310 a and 310 b located in two pixel areas 320sharing a corner. The sub-pixel electrodes 310 a and 310 b are connectedto each other through a connecting part 310 c. Similarly, pixelelectrode 315 comprises two sub-pixel electrodes 315 a, 315 b located intwo pixel areas 320 sharing a corner. The sub-pixel electrodes 315 a and315 b are connected to each other through a connecting part 315 c.Therefore, a repeating unit of a pattern formed by the first sub-pixelelectrodes 310 a, 310 b and the second sub-pixel electrodes 315 a, 315 bis two first sub-pixel electrodes 310 a, 310 b located in the twoopposite edges of a parallelogram and two second sub-pixel electrodes315 a, 315 b located in the other two opposite edges of theparallelogram.

The above mentioned pixel area 320 is defined by a pair of scan line 330and a pair of data line 340. A switch device 350 is formed in one cornerof the pixel area 320. The switch device 350 in this embodiment is athin film transistor with a gate, a source and a drain connected to thescan line 330, the data line 340, the sub-pixel electrode 310 a or 315a, respectively.

The pixel electrodes 310, 315 shown in FIG. 3 are formed on a switchdevice substrate alternatively. The two neighboring pixel electrodes310, 315 can be controlled to have opposite polarities, so that the samepixel area 320 comprising two sub-pixel electrodes 310 b, 315 a (or 315b, 310 a) with opposite polarities can be obtained. Although the twosub-pixel electrodes 310 b, 315 a (or 315 b, 310 a) in one pixel area320 belong to two different pixel electrodes 315 and 310, the twosub-pixel electrodes 310 a, 310 b (or 315 a, 315 b) belonged the pixelelectrode 310 (or 315) are still connected to each other through theconnecting part 310 c. Hence, only one switch device is required todrive the pixel electrode 310 (or 315). In addition, dot inversionmethod or any appropriate method can be used to allow the twoneighboring pixel electrodes 310, 315 to have opposite polarities.

The above mentioned pixel array structure can be applied to any flatpanel display, for example, LCD. Referring to FIG. 4, an LCD 400comprises a lower substrate 410, an upper substrate 420 and a liquidcrystal layer 430 disposed therebetween. There are many possiblemodifications for the lower substrate 410 and the upper substrate 420 ofrecent LCD 400 products. For the first example, the upper substrate 420can be a color filter if the lower substrate 410 is a control circuitboard. For the second example, the control circuit board and the colorfilter layer can be formed on the lower substrate 410, and there is onlya common electrode layer on the upper substrate 420. Based on thelocation of the control circuit and the color filter, the structure canbe either COA (Color Filter on Array) or AOC (Array on Color Filter).The detailed structures of COA and AOC are not shown in FIG. 4 becausethese possible modifications are apparent to those skilled in the art.

Accordingly, the pixel electrode is only divided into severalstructurally connected sub-pixel electrodes. Only one driving switchdevice is required for one pixel. Furthermore, pixel electrodes withopposite polarities are alternatively arranged. At least two sub-pixelelectrodes can be formed on each pixel area without additional signalline and driving switch device.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structures of thepresent invention without departing from the scope or spirit thereof. Inview of the foregoing, it is intended that the present invention covermodifications and variations thereof provided they fall within the scopeof the following claims.

1. A liquid crystal display (LCD), comprising: an upper substrate; alower substrate comprising a pixel array having plural first pixel areasand plural second pixel areas arranged alternatively, each of the firstpixel areas and the second pixel areas being defined by a pair of scanlines and a pair of data lines, the pixel array comprising: plural firstpixel electrodes, each of the first pixel electrodes comprising a firstconnecting part and two first sub-pixel electrodes, each first sub-pixelelectrode having at least three corners, the two first sub-pixelelectrodes being diagonally connected through the first connecting partat respective corners of the two first sub-pixel electrodes andseparately located on one of the first pixel areas and one of the secondpixel areas located adjacently; plural second pixel electrodes, each ofthe second pixel electrodes comprising a second connecting part and twosecond sub-pixel electrodes, each second sub-pixel electrode having atleast three corners, the two second sub-pixel electrodes beingdiagonally connected through the second connecting part at respectivecorners of the two second sub-pixel electrodes and separately located onone of the first pixel areas and one of the second pixel areas locatedadjacently in such a manner that one of the two first sub-pixelelectrodes and one of the two second sub-pixel electrodes are disposedside by side in a same one of the first pixel areas or in a same one ofthe second pixel areas, wherein the second pixel electrode and the firstpixel electrode have opposite polarities; and plural first switches,disposed on the first pixel areas, for controlling the first pixelelectrodes, respectively; plural second switches, disposed on the secondpixel areas, for controlling the second pixel electrodes, respectively;and a liquid crystal layer interposed between the upper substrate andthe lower substrate.
 2. The LCD of claim 1, wherein the repeating unitof the pattern formed by the first sub-pixel electrodes and the secondsub-pixel electrodes is two first sub-pixel electrodes in the twodiagonal areas of a parallelogram and two second sub-pixel electrodes inthe other two diagonal areas of the parallelogram.
 3. The LCD of claim1, wherein a repeating unit of a pattern formed by the first sub-pixelelectrodes and the second sub-pixel electrodes is two first sub-pixelelectrodes located in the two opposite edges of a parallelogram and twosecond sub-pixel electrodes located in the other two opposite edges ofthe parallelogram.
 4. The LCD of claim 1, wherein the two adjacent pixelareas sharing a corner.
 5. The LCD of claim 1, wherein the two adjacentpixel areas sharing an edge.
 6. The LCD of claim 1, further comprising aplurality of scan lines and a plurality of data lines connected to theswitch devices on the substrate.